The present invention relates to all terrain vehicles. More particularly, the present invention relates to an all terrain vehicle employing an endless track, such as for example a snowmobile, in which an engine is positioned within the endless track.
For more than the past fifty years, snowmobiling has been an ever increasing way of pleasure travel in winter time climates, especially in snow covered regions of the world. Examples of early snowmobiles include U.S. Pat. No. 2,289,768, which was a motorized snow sled wherein the driver rode a sled on the ground while being pulled by a tracked locomotive.
Several advancements in the art have occurred since then, however the drive system components in the past 45 years are still the same style of components and are still in generally the same locations. Modern day snowmobiles generally include a forward positioned engine on skis powering a belt driven continuous variable transmission (“CVT”), which in turn powers a jackshaft which drives a chain to the drive roller axle which propels the endless track via engagement lugs on the endless track. Generally the CVT is on one side of the endless track and the chain is on the opposite side of the track and both components add width beyond that of the endless track width. The overall system efficiency of the industry accepted drive system has resulted in the need for high horsepower engines in order to achieve a high performance snowmobile. Therefore the primary engine of choice is a liquid cooled engine to achieve the highest possible power-to-weight ratio. Positioning the engine as low as possible forward of the endless track has become the normal location. Associated complementary drive components are generally located between the engine and front drive roller.
Endless tracks of the prior art are generally supported by five components which create the geometry of the pathway in which the endless track profile is defined by. Generally the shape of the profile is a parallelogram having a front driver roller of between and 7 to 9 inches and several idler rollers having diameters between 6 to 8 inches. When the suspension of the skid frame is compressed the track profile becomes more of an oval shape. The industry standard location of the drive roller is at the front of the endless track which is an inefficient location for propelling the snowmobile forward as approximately 85-90% of the endless track is under load. Another component of the endless track is tensile cords that are molded within the rubber to help prevent the track from stretching under load. While these cords help to minimize the stored energy of the rubber under load, they add to the energy needed to bend the endless track around the drive roller and corresponding idler rollers traveling around its defined pathway. The bend angles based on the pitch length of the endless track on typical snowmobiles can vary between 17-22° with corresponding 9 or 7 inch drive wheel and 8 or 6 inch rear idler rollers on the skid rail. Therefore the more length the endless track is under load and the greater the bend angle the more energy losses there are to propel the endless track. These are two large factors that influence the overall vehicle efficiency. Further, the preset endless track tightness of current snowmobiles must be properly maintained by the user because if the endless track becomes too loose the drive roller engagement of the endless track lugs can skip under load resulting in loss of acceleration. This preset endless track tightness also lends itself to more energy being put into the endless track to travel along its defined pathway. With the aforementioned considerations in mind, overall system efficiency of modern snowmobiles is approximately 50-55%, which has become generally accepted. To compensate for these efficiency losses, the industry generally makes high horsepower engines to produce a popular vehicle to ride.
In recent years, snowmobile manufacturers have been attempting designs which make the snowmobile more nimble and agile. Such designs include attempting to bring the riding position of the rider forward towards the skis. However, the current engine and corresponding drive components locations in snowmobiles of the prior art has limited how far forward the rider can sit. The placement of the engine relative to the endless track has also controlled the location of the gas tank, as it is typically located directly above the endless track relative to the ground. Further, as all snowmobiles with a belt drive CVT, jackshaft, and chain to the drive roller axle, these components are positioned on the outside of the track width, thereby inhibiting the streamlining of the snowmobile.
Another fixed condition of current snowmobile designs includes the positioning of the rider's feet. As snowmobiles tend to place the rider directly above the endless track, the legs and feet of the rider must be spaced apart at least as wide as the width of the track.
Another concern inherent with current endless track designs of liquid cooled snowmobiles is that they do not offer any possibility for driving in non-snow terrains for long durations. Because of the power losses associated in their inefficient drive system design, the necessary heat rejection of the engine is typically dependant on snow as a cooling agent to keep engines at their regular operating temperatures.
Finally, an overriding concern for all snowmobile manufacturers and riders is the smoothness and comfort of the ride. While there have been advances in suspension systems, especially over the last 25 years, none have been able to adequately provide a progressively linked rear suspension system for both the rear and front portions of the skid frame.
There therefore exists a need in the art to overcome these shortcomings. It is therefore an object of the present invention to provide an all terrain endless track vehicle with improved overall system efficiency in order to use an engine with less horsepower. It is also an object of the present invention to provide an endless track vehicle having more options for both the front and rear portions of the skid frame suspension. It is also an object of the present invention to provide an endless track vehicle having more options for the rider position. It is also an object of the present invention to provide an endless track vehicle having a more centralized center of mass as well as a lower center of mass for the overall vehicle. It is a further object of the present invention to provide an all terrain endless track vehicle having an engine positioned within an endless track. It is a further object of the present invention to provide an all terrain endless track vehicle operable in a variety of terrains, including non-snow terrains. It is an even further object of the present invention to provide an all terrain endless track vehicle operable in a wide range of temperature conditions, including temperate climates.